Volume 2 of the Illustrated Checklist of the Handbook of the Birds of the World covers 6,592 extant and 57 extinct passerines. It is a companion to the volume of non-passerines issued in 2016, and together they present a full evaluation of the world’s bird species (a total of 10,964 over the two volumes). In structure and format, this book follows the layout of Volume 1: a short introduction then 446 colour plates with 12,629 illustrations and accompanying text for each species.

For me, the major attraction of these volumes is that they present all species for each genus/family in one place, but in the format of a field guide. This is something that regional guides can’t do, and so the Checklist provides a unique perspective of diversity within each group. The text for each species is necessarily brief though, and most readers will need to go elsewhere if they need information beyond a species’ distribution and its subspecies.

Rigorous application of the Tobias criteria in species delimitation has led to an increase of over 500 passerine species since the publication of the full Handbook of the Birds of the World, and this has led to some interesting outcomes. For instance, the Red-bellied Pitta of old has been split into 13 species—while each is clearly different in the illustrations, they are all geographically isolated, so birders are still likely to see the ‘Red-bellied Pitta’ that occurs wherever they are.

Where splitting under the Tobias criteria might have more relevance is when new species have been evaluated for their threat level against IUCN criteria. As most have a smaller geographic range than the original species-complex, some have a corresponding higher threat rating (for the Red-bellied Pitta, two of the new species are Endangered). This higher rating should confer better protection, although only time will tell if this is the case.

So, should you buy this volume? If you have Volume 1, then you must have this—they are a pair after all. If you decided not to buy Volume 1, then nothing in this one will change your mind.